Update the permission checks to use the new uid_eq and gid_eq helpers
and remove the now unnecessary user_ns equality comparison.
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Optimize performance and prepare for the removal of the user_ns reference
from user_struct.  Remove the slow long walk through cred->user->user_ns and
instead go straight to cred->user_ns.
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

PTRACE_SEIZE code is tested and ready for production use, remove the
code which requires special bit in data argument to make PTRACE_SEIZE
work.

Strace team prepares for a new release of strace, and we would like to
ship the code which uses PTRACE_SEIZE, preferably after this change goes
into released kernel.
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This can be used to close a few corner cases in strace where we get
unwanted racy behavior after attach, but before we have a chance to set
options (the notorious post-execve SIGTRAP comes to mind), and removes
the need to track "did we set opts for this task" state in strace
internals.

While we are at it:

Make it possible to extend SEIZE in the future with more functionality
by passing non-zero 'addr' parameter.  To that end, error out if 'addr'
is non-zero.  PTRACE_ATTACH did not (and still does not) have such
check, and users (strace) do pass garbage there...  let's avoid
repeating this mistake with SEIZE.

Set all task->ptrace bits in one operation - before this change, we were
adding PT_SEIZED and PT_PTRACE_CAP with task->ptrace |= BIT ops.  This
was probably ok (not a bug), but let's be on a safer side.

Changes since v2: use (unsigned long) casts instead of (long) ones, move
PTRACE_SEIZE_DEVEL-related code to separate lines of code.
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Cc: Pedro Alves <palves@redhat.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Exchange PT_TRACESYSGOOD and PT_PTRACE_CAP bit positions, which makes
PT_option bits contiguous and therefore makes code in
ptrace_setoptions() much simpler.

Every PTRACE_O_TRACEevent is defined to (1 << PTRACE_EVENT_event)
instead of using explicit numeric constants, to ensure we don't mess up
relationship between bit positions and event ids.

PT_EVENT_FLAG_SHIFT was not particularly useful, PT_OPT_FLAG_SHIFT with
value of PT_EVENT_FLAG_SHIFT-1 is easier to use.

PT_TRACE_MASK constant is nuked, the only its use is replaced by
(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT).
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

On ptrace(PTRACE_SETOPTIONS, pid, 0, <opts>), we used to set those
option bits which are known, and then fail with -EINVAL if there are
some unknown bits in <opts>.

This is inconsistent with typical error handling, which does not change
any state if input is invalid.

This patch changes PTRACE_SETOPTIONS behavior so that in this case, we
return -EINVAL and don't change any bits in task->ptrace.

It's very unlikely that there is userspace code in the wild which will
be affected by this change: it should have the form

    ptrace(PTRACE_SETOPTIONS, pid, 0, PTRACE_O_BOGUSOPT)

where PTRACE_O_BOGUSOPT is a constant unknown to the kernel.  But kernel
headers, naturally, don't contain any PTRACE_O_BOGUSOPTs, thus the only
way userspace can use one if it defines one itself.  I can't see why
anyone would do such a thing deliberately.
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Reading /proc/pid/stat of another process checks if one has ptrace permissions
on that process.  If one does have permissions it outputs some data about the
process which might have security and attack implications.  If the current
task does not have ptrace permissions the read still works, but those fields
are filled with inocuous (0) values.  Since this check and a subsequent denial
is not a violation of the security policy we should not audit such denials.

This can be quite useful to removing ptrace broadly across a system without
flooding the logs when ps is run or something which harmlessly walks proc.
Signed-off-by: NEric Paris <eparis@redhat.com>
Acked-by: NSerge E. Hallyn <serge.hallyn@canonical.com>

task_ in the front of a function, in the security subsystem anyway, means
to me at least, that we are operating with that task as the subject of the
security decision.  In this case what it means is that we are using current as
the subject but we use the task to get the right namespace.  Who in the world
would ever realize that's what task_ns_capability means just by the name?  This
patch eliminates the task_ns functions entirely and uses the has_ns_capability
function instead.  This means we explicitly open code the ns in question in
the caller.  I think it makes the caller a LOT more clear what is going on.
Signed-off-by: NEric Paris <eparis@redhat.com>
Acked-by: NSerge E. Hallyn <serge.hallyn@canonical.com>

This is the temporary simple fix for 3.2, we need more changes in this
area.

1. do_signal_stop() assumes that the running untraced thread in the
   stopped thread group is not possible. This was our goal but it is
   not yet achieved: a stopped-but-resumed tracee can clone the running
   thread which can initiate another group-stop.

   Remove WARN_ON_ONCE(!current->ptrace).

2. A new thread always starts with ->jobctl = 0. If it is auto-attached
   and this group is stopped, __ptrace_unlink() sets JOBCTL_STOP_PENDING
   but JOBCTL_STOP_SIGMASK part is zero, this triggers WANR_ON(!signr)
   in do_jobctl_trap() if another debugger attaches.

   Change __ptrace_unlink() to set the artificial SIGSTOP for report.

   Alternatively we could change ptrace_init_task() to copy signr from
   current, but this means we can copy it for no reason and hide the
   possible similar problems.
Acked-by: NTejun Heo <tj@kernel.org>
Cc: <stable@kernel.org>		[3.1]
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The changed files were only including linux/module.h for the
EXPORT_SYMBOL infrastructure, and nothing else.  Revector them
onto the isolated export header for faster compile times.

Nothing to see here but a whole lot of instances of:

  -#include <linux/module.h>
  +#include <linux/export.h>

This commit is only changing the kernel dir; next targets
will probably be mm, fs, the arch dirs, etc.
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

If PTRACE_LISTEN fails after lock_task_sighand() it doesn't drop ->siglock.
Reported-by: NMatt Fleming <matt.fleming@intel.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This change adds a procfs connector event, which is emitted on every
successful process tracer attach or detach.

If some process connects to other one, kernelspace connector reports
process id and thread group id of both these involved processes. On
disconnection null process id is returned.

Such an event allows to create a simple automated userspace mechanism
to be aware about processes connecting to others, therefore predefined
process policies can be applied to them if needed.

Note, a detach signal is emitted only in case, if a tracer process
explicitly executes PTRACE_DETACH request. In other cases like tracee
or tracer exit detach event from proc connector is not reported.
Signed-off-by: NVladimir Zapolskiy <vzapolskiy@gmail.com>
Acked-by: NEvgeniy Polyakov <zbr@ioremap.net>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

__ptrace_detach() and do_notify_parent() set task->exit_signal = -1
to mark the task dead. This is no longer needed, nobody checks
exit_signal to detect the EXIT_DEAD task.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NTejun Heo <tj@kernel.org>

__ptrace_detach() relies on the current obscure behaviour of
do_notify_parent(tsk) which changes tsk->exit_signal if this child
should be silently reaped. That is why we check task_detached(), it
is true if the task is sub-thread, or it is the group_leader but
its exit_signal was changed by do_notify_parent().

This is confusing, change the code to rely on !thread_group_leader()
or the value returned by do_notify_parent().
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NTejun Heo <tj@kernel.org>

The previous patch implemented async notification for ptrace but it
only worked while trace is running.  This patch introduces
PTRACE_LISTEN which is suggested by Oleg Nestrov.

It's allowed iff tracee is in STOP trap and puts tracee into
quasi-running state - tracee never really runs but wait(2) and
ptrace(2) consider it to be running.  While ptracer is listening,
tracee is allowed to re-enter STOP to notify an async event.
Listening state is cleared on the first notification.  Ptracer can
also clear it by issuing INTERRUPT - tracee will re-trap into STOP
with listening state cleared.

This allows ptracer to monitor group stop state without running tracee
- use INTERRUPT to put tracee into STOP trap, issue LISTEN and then
wait(2) to wait for the next group stop event.  When it happens,
PTRACE_GETSIGINFO provides information to determine the current state.

Test program follows.

  #define PTRACE_SEIZE		0x4206
  #define PTRACE_INTERRUPT	0x4207
  #define PTRACE_LISTEN		0x4208

  #define PTRACE_SEIZE_DEVEL	0x80000000

  static const struct timespec ts1s = { .tv_sec = 1 };

  int main(int argc, char **argv)
  {
	  pid_t tracee, tracer;
	  int i;

	  tracee = fork();
	  if (!tracee)
		  while (1)
			  pause();

	  tracer = fork();
	  if (!tracer) {
		  siginfo_t si;

		  ptrace(PTRACE_SEIZE, tracee, NULL,
			 (void *)(unsigned long)PTRACE_SEIZE_DEVEL);
		  ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL);
	  repeat:
		  waitid(P_PID, tracee, NULL, WSTOPPED);

		  ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si);
		  if (!si.si_code) {
			  printf("tracer: SIG %d\n", si.si_signo);
			  ptrace(PTRACE_CONT, tracee, NULL,
				 (void *)(unsigned long)si.si_signo);
			  goto repeat;
		  }
		  printf("tracer: stopped=%d signo=%d\n",
			 si.si_signo != SIGTRAP, si.si_signo);
		  if (si.si_signo != SIGTRAP)
			  ptrace(PTRACE_LISTEN, tracee, NULL, NULL);
		  else
			  ptrace(PTRACE_CONT, tracee, NULL, NULL);
		  goto repeat;
	  }

	  for (i = 0; i < 3; i++) {
		  nanosleep(&ts1s, NULL);
		  printf("mother: SIGSTOP\n");
		  kill(tracee, SIGSTOP);
		  nanosleep(&ts1s, NULL);
		  printf("mother: SIGCONT\n");
		  kill(tracee, SIGCONT);
	  }
	  nanosleep(&ts1s, NULL);

	  kill(tracer, SIGKILL);
	  kill(tracee, SIGKILL);
	  return 0;
  }

This is identical to the program to test TRAP_NOTIFY except that
tracee is PTRACE_LISTEN'd instead of PTRACE_CONT'd when group stopped.
This allows ptracer to monitor when group stop ends without running
tracee.

  # ./test-listen
  tracer: stopped=0 signo=5
  mother: SIGSTOP
  tracer: SIG 19
  tracer: stopped=1 signo=19
  mother: SIGCONT
  tracer: stopped=0 signo=5
  tracer: SIG 18
  mother: SIGSTOP
  tracer: SIG 19
  tracer: stopped=1 signo=19
  mother: SIGCONT
  tracer: stopped=0 signo=5
  tracer: SIG 18
  mother: SIGSTOP
  tracer: SIG 19
  tracer: stopped=1 signo=19
  mother: SIGCONT
  tracer: stopped=0 signo=5
  tracer: SIG 18

-v2: Moved JOBCTL_LISTENING check in wait_task_stopped() into
     task_stopped_code() as suggested by Oleg.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>

Currently, there's no way to trap a running ptracee short of sending a
signal which has various side effects.  This patch implements
PTRACE_INTERRUPT which traps ptracee without any signal or job control
related side effect.

The implementation is almost trivial.  It uses the group stop trap -
SIGTRAP | PTRACE_EVENT_STOP << 8.  A new trap flag
JOBCTL_TRAP_INTERRUPT is added, which is set on PTRACE_INTERRUPT and
cleared when any trap happens.  As INTERRUPT should be useable
regardless of the current state of tracee, task_is_traced() test in
ptrace_check_attach() is skipped for INTERRUPT.

PTRACE_INTERRUPT is available iff tracee is attached with
PTRACE_SEIZE.

Test program follows.

  #define PTRACE_SEIZE		0x4206
  #define PTRACE_INTERRUPT	0x4207

  #define PTRACE_SEIZE_DEVEL	0x80000000

  static const struct timespec ts100ms = { .tv_nsec = 100000000 };
  static const struct timespec ts1s = { .tv_sec = 1 };
  static const struct timespec ts3s = { .tv_sec = 3 };

  int main(int argc, char **argv)
  {
	  pid_t tracee;

	  tracee = fork();
	  if (tracee == 0) {
		  nanosleep(&ts100ms, NULL);
		  while (1) {
			  printf("tracee: alive pid=%d\n", getpid());
			  nanosleep(&ts1s, NULL);
		  }
	  }

	  if (argc > 1)
		  kill(tracee, SIGSTOP);

	  nanosleep(&ts100ms, NULL);

	  ptrace(PTRACE_SEIZE, tracee, NULL,
		 (void *)(unsigned long)PTRACE_SEIZE_DEVEL);
	  if (argc > 1) {
		  waitid(P_PID, tracee, NULL, WSTOPPED);
		  ptrace(PTRACE_CONT, tracee, NULL, NULL);
	  }
	  nanosleep(&ts3s, NULL);

	  printf("tracer: INTERRUPT and DETACH\n");
	  ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL);
	  waitid(P_PID, tracee, NULL, WSTOPPED);
	  ptrace(PTRACE_DETACH, tracee, NULL, NULL);
	  nanosleep(&ts3s, NULL);

	  printf("tracer: exiting\n");
	  kill(tracee, SIGKILL);
	  return 0;
  }

When called without argument, tracee is seized from running state,
interrupted and then detached back to running state.

  # ./test-interrupt
  tracee: alive pid=4546
  tracee: alive pid=4546
  tracee: alive pid=4546
  tracer: INTERRUPT and DETACH
  tracee: alive pid=4546
  tracee: alive pid=4546
  tracee: alive pid=4546
  tracer: exiting

When called with argument, tracee is seized from stopped state,
continued, interrupted and then detached back to stopped state.

  # ./test-interrupt  1
  tracee: alive pid=4548
  tracee: alive pid=4548
  tracee: alive pid=4548
  tracer: INTERRUPT and DETACH
  tracer: exiting

Before PTRACE_INTERRUPT, once the tracee was running, there was no way
to trap tracee and do PTRACE_DETACH without causing side effect.

-v2: Updated to use task_set_jobctl_pending() so that it doesn't end
     up scheduling TRAP_STOP if child is dying which may make the
     child unkillable.  Spotted by Oleg.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>

PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side
effects on tracee signal and job control states.  This patch
implements a new ptrace request PTRACE_SEIZE which attaches a tracee
without trapping it or affecting its signal and job control states.

The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_*
flags in @data.  Currently, the only defined flag is
PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE.
PTRACE_SEIZE will change ptrace behaviors outside of attach itself.
The changes will be implemented gradually and the DEVEL flag is to
prevent programs which expect full SEIZE behavior from using it before
all the behavior modifications are complete while allowing unit
testing.  The flag will be removed once SEIZE behaviors are completely
implemented.

* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap.  After
  attaching tracee continues to run unless a trap condition occurs.

* PTRACE_SEIZE doesn't affect signal or group stop state.

* If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses
  exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of
  the stopping signals if group stop is in effect or SIGTRAP
  otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO
  instead of NULL.

Seizing sets PT_SEIZED in ->ptrace of the tracee.  This flag will be
used to determine whether new SEIZE behaviors should be enabled.

Test program follows.

  #define PTRACE_SEIZE		0x4206
  #define PTRACE_SEIZE_DEVEL	0x80000000

  static const struct timespec ts100ms = { .tv_nsec = 100000000 };
  static const struct timespec ts1s = { .tv_sec = 1 };
  static const struct timespec ts3s = { .tv_sec = 3 };

  int main(int argc, char **argv)
  {
	  pid_t tracee;

	  tracee = fork();
	  if (tracee == 0) {
		  nanosleep(&ts100ms, NULL);
		  while (1) {
			  printf("tracee: alive\n");
			  nanosleep(&ts1s, NULL);
		  }
	  }

	  if (argc > 1)
		  kill(tracee, SIGSTOP);

	  nanosleep(&ts100ms, NULL);

	  ptrace(PTRACE_SEIZE, tracee, NULL,
		 (void *)(unsigned long)PTRACE_SEIZE_DEVEL);
	  if (argc > 1) {
		  waitid(P_PID, tracee, NULL, WSTOPPED);
		  ptrace(PTRACE_CONT, tracee, NULL, NULL);
	  }
	  nanosleep(&ts3s, NULL);
	  printf("tracer: exiting\n");
	  return 0;
  }

When the above program is called w/o argument, tracee is seized while
running and remains running.  When tracer exits, tracee continues to
run and print out messages.

  # ./test-seize-simple
  tracee: alive
  tracee: alive
  tracee: alive
  tracer: exiting
  tracee: alive
  tracee: alive

When called with an argument, tracee is seized from stopped state and
continued, and returns to stopped state when tracer exits.

  # ./test-seize
  tracee: alive
  tracee: alive
  tracee: alive
  tracer: exiting
  # ps -el|grep test-seize
  1 T     0  4720     1  0  80   0 -   941 signal ttyS0    00:00:00 test-seize

-v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan
     suggested.

-v3: PTRACE_EVENT_STOP traps now report group stop state by signr.  If
     group stop is in effect the stop signal number is returned as
     part of exit_code; otherwise, SIGTRAP.  This was suggested by
     Denys and Oleg.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Oleg Nesterov <oleg@redhat.com>

do_signal_stop() implemented both normal group stop and trap for group
stop while ptraced.  This approach has been enough but scheduled
changes require trap mechanism which can be used in more generic
manner and using group stop trap for generic trap site simplifies both
userland visible interface and implementation.

This patch adds a new jobctl flag - JOBCTL_TRAP_STOP.  When set, it
triggers a trap site, which behaves like group stop trap, in
get_signal_to_deliver() after checking for pending signals.  While
ptraced, do_signal_stop() doesn't stop itself.  It initiates group
stop if requested and schedules JOBCTL_TRAP_STOP and returns.  The
caller - get_signal_to_deliver() - is responsible for checking whether
TRAP_STOP is pending afterwards and handling it.

ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of
JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap
bits and TRAPPING so that TRAP_STOP and future trap bits don't linger
after detach.

While at it, add proper function comment to do_signal_stop() and make
it return bool.

-v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING
     instead of JOBCTL_PENDING_MASK.  This avoids accidentally
     clearing JOBCTL_STOP_CONSUME.  Spotted by Oleg.

-v3: do_signal_stop() updated to return %false without dropping
     siglock while ptraced and TRAP_STOP check moved inside for(;;)
     loop after group stop participation.  This avoids unnecessary
     relocking and also will help avoiding unnecessary traps by
     consuming group stop before handling pending traps.

-v4: Jobctl trap handling moved into a separate function -
     do_jobctl_trap().
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>

ptracer->signal->wait_chldexit was used to wait for TRAPPING; however,
->wait_chldexit was already complicated with waker-side filtering
without adding TRAPPING wait on top of it.  Also, it unnecessarily
made TRAPPING clearing depend on the current ptrace relationship - if
the ptracee is detached, wakeup is lost.

There is no reason to use signal->wait_chldexit here.  We're just
waiting for JOBCTL_TRAPPING bit to clear and given the relatively
infrequent use of ptrace, bit_waitqueue can serve it perfectly.

This patch makes JOBCTL_TRAPPING wait use bit_waitqueue instead of
signal->wait_chldexit.

-v2: Use JOBCTL_*_BIT macros instead of ilog2() as suggested by Linus.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

task->jobctl currently hosts JOBCTL_STOP_PENDING and will host TRAP
pending bits too.  Setting pending conditions on a dying task may make
the task unkillable.  Currently, each setting site is responsible for
checking for the condition but with to-be-added job control traps this
becomes too fragile.

This patch adds task_set_jobctl_pending() which should be used when
setting task->jobctl bits to schedule a stop or trap.  The function
performs the followings to ease setting pending bits.

* Sanity checks.

* If fatal signal is pending or PF_EXITING is set, no bit is set.

* STOP_SIGMASK is automatically cleared if new value is being set.

do_signal_stop() and ptrace_attach() are updated to use
task_set_jobctl_pending() instead of setting STOP_PENDING explicitly.
The surrounding structures around setting are changed to fit
task_set_jobctl_pending() better but there should be no userland
visible behavior difference.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

PTRACE_INTERRUPT is going to be added which should also skip
task_is_traced() check in ptrace_check_attach().  Rename @kill to
@ignore_state and make it bool.  Add function comment while at it.

This patch doesn't introduce any behavior difference.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

signal->group_stop currently hosts mostly group stop related flags;
however, it's gonna be used for wider purposes and the GROUP_STOP_
flag prefix becomes confusing.  Rename signal->group_stop to
signal->jobctl and rename all GROUP_STOP_* flags to JOBCTL_*.

Bit position macros JOBCTL_*_BIT are defined and JOBCTL_* flags are
defined in terms of them to allow using bitops later.

While at it, reassign JOBCTL_TRAPPING to bit 22 to better accomodate
future additions.

This doesn't cause any functional change.

-v2: JOBCTL_*_BIT macros added as suggested by Linus.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

Remove local variable wait_trap which determines whether to wait for
!TRAPPING or not and simply wait for it if attach was successful.

-v2: Oleg pointed out wait should happen iff attach was successful.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

It is not clear why ptrace_resume() does wake_up_process(). Unless the
caller is PTRACE_KILL the tracee should be TASK_TRACED so we can use
wake_up_state(__TASK_TRACED). If sys_ptrace() races with SIGKILL we do
not need the extra and potentionally spurious wakeup.

If the caller is PTRACE_KILL, wake_up_process() is even more wrong.
The tracee can sleep in any state in any place, and if we have a buggy
code which doesn't handle a spurious wakeup correctly PTRACE_KILL can
be used to exploit it. For example:

	int main(void)
	{
		int child, status;

		child = fork();
		if (!child) {
			int ret;

			assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0);

			ret = pause();
			printf("pause: %d %m\n", ret);

			return 0x23;
		}

		sleep(1);
		assert(ptrace(PTRACE_KILL, child, 0,0) == 0);

		assert(child == wait(&status));
		printf("wait: %x\n", status);

		return 0;
	}

prints "pause: -1 Unknown error 514", -ERESTARTNOHAND leaks to the
userland. In this case sys_pause() is buggy as well and should be
fixed.

I do not know what was the original rationality behind PTRACE_KILL.
The man page is simply wrong and afaics it was always wrong. Imho
it should be deprecated, or may be it should do send_sig(SIGKILL)
as Denys suggests, but in any case I do not think that the current
behaviour was intentional.

Note: there is another problem, ptrace_resume() changes ->exit_code
and this can race with SIGKILL too. Eventually we should change ptrace
to not use ->exit_code.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

When a task is traced and is in a stopped state, the tracer
may execute a ptrace request to examine the tracee state and
get its task struct. Right after, the tracee can be killed
and thus its breakpoints released.
This can happen concurrently when the tracer is in the middle
of reading or modifying these breakpoints, leading to dereferencing
a freed pointer.

Hence, to prepare the fix, create a generic breakpoint reference
holding API. When a reference on the breakpoints of a task is
held, the breakpoints won't be released until the last reference
is dropped. After that, no more ptrace request on the task's
breakpoints can be serviced for the tracer.
Reported-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: v2.6.33.. <stable@kernel.org>
Link: http://lkml.kernel.org/r/1302284067-7860-2-git-send-email-fweisbec@gmail.com

After "ptrace: Clean transitions between TASK_STOPPED and TRACED"
d79fdd6d, ptrace_check_attach()
should never see a TASK_STOPPED tracee and s/STOPPED/TRACED/ is
no longer legal. Add the warning.

Note: ptrace_check_attach() can be greatly simplified, in particular
it doesn't need tasklist. But I'd prefer another patch for that.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

ptrace is allowed to tasks in the same user namespace according to the
usual rules (i.e.  the same rules as for two tasks in the init user
namespace).  ptrace is also allowed to a user namespace to which the
current task the has CAP_SYS_PTRACE capability.

Changelog:
	Dec 31: Address feedback by Eric:
		. Correct ptrace uid check
		. Rename may_ptrace_ns to ptrace_capable
		. Also fix the cap_ptrace checks.
	Jan  1: Use const cred struct
	Jan 11: use task_ns_capable() in place of ptrace_capable().
	Feb 23: same_or_ancestore_user_ns() was not an appropriate
		check to constrain cap_issubset.  Rather, cap_issubset()
		only is meaningful when both capsets are in the same
		user_ns.
Signed-off-by: NSerge E. Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: NDaniel Lezcano <daniel.lezcano@free.fr>
Acked-by: NDavid Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, __ptrace_unlink() wakes up the tracee iff it's in
TASK_TRACED.  For unlinking from PTRACE_DETACH, this is correct as the
tracee is guaranteed to be in TASK_TRACED or dead; however, unlinking
also happens when the ptracer exits and in this case the ptracee can
be in any state and ptrace might be left running even if the group it
belongs to is stopped.

This patch updates __ptrace_unlink() such that GROUP_STOP_PENDING is
reinstated regardless of the ptracee's current state as long as it's
alive and makes sure that signal_wake_up() is called if execution
state transition is necessary.

Test case follows.

  #include <unistd.h>
  #include <time.h>
  #include <sys/types.h>
  #include <sys/ptrace.h>
  #include <sys/wait.h>

  static const struct timespec ts1s = { .tv_sec = 1 };

  int main(void)
  {
	  pid_t tracee;
	  siginfo_t si;

	  tracee = fork();
	  if (tracee == 0) {
		  while (1) {
			  nanosleep(&ts1s, NULL);
			  write(1, ".", 1);
		  }
	  }

	  ptrace(PTRACE_ATTACH, tracee, NULL, NULL);
	  waitid(P_PID, tracee, &si, WSTOPPED);
	  ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status);
	  waitid(P_PID, tracee, &si, WSTOPPED);
	  ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status);
	  write(1, "exiting", 7);
	  return 0;
  }

Before the patch, after the parent process exits, the child is left
running and prints out "." every second.

  exiting..... (continues)

After the patch, the group stop initiated by the implied SIGSTOP from
PTRACE_ATTACH is re-established when the parent exits.

  exiting
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NOleg Nesterov <oleg@redhat.com>

Remove the extra task_is_traced() check in __ptrace_unlink() and
collapse ptrace_untrace() into __ptrace_unlink().  This is to prepare
for further changes.

While at it, drop the comment on top of ptrace_untrace() and convert
__ptrace_unlink() comment to docbook format.  Detailed comment will be
added by the next patch.

This patch doesn't cause any visible behavior changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>

Currently, if the task is STOPPED on ptrace attach, it's left alone
and the state is silently changed to TRACED on the next ptrace call.
The behavior breaks the assumption that arch_ptrace_stop() is called
before any task is poked by ptrace and is ugly in that a task
manipulates the state of another task directly.

With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and
TRACED can be made clean.  The tracer can use the flag to tell the
tracee to retry stop on attach and detach.  On retry, the tracee will
enter the desired state in the correct way.  The lower 16bits of
task->group_stop is used to remember the signal number which caused
the last group stop.  This is used while retrying for ptrace attach as
the original group_exit_code could have been consumed with wait(2) by
then.

As the real parent may wait(2) and consume the group_exit_code
anytime, the group_exit_code needs to be saved separately so that it
can be used when switching from regular sleep to ptrace_stop().  This
is recorded in the lower 16bits of task->group_stop.

If a task is already stopped and there's no intervening SIGCONT, a
ptrace request immediately following a successful PTRACE_ATTACH should
always succeed even if the tracer doesn't wait(2) for attach
completion; however, with this change, the tracee might still be
TASK_RUNNING trying to enter TASK_TRACED which would cause the
following request to fail with -ESRCH.

This intermediate state is hidden from the ptracer by setting
GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait
for it to clear on its signal->wait_chldexit.  Completing the
transition or getting killed clears TRAPPING and wakes up the tracer.

Note that the STOPPED -> RUNNING -> TRACED transition is still visible
to other threads which are in the same group as the ptracer and the
reverse transition is visible to all.  Please read the comments for
details.

Oleg:

* Spotted a race condition where a task may retry group stop without
  proper bookkeeping.  Fixed by redoing bookkeeping on retry.

* Spotted that the transition is visible to userland in several
  different ways.  Most are fixed with GROUP_STOP_TRAPPING.  Unhandled
  corner case is documented.

* Pointed out not setting GROUP_STOP_SIGMASK on an already stopped
  task would result in more consistent behavior.

* Pointed out that calling ptrace_stop() from do_signal_stop() in
  TASK_STOPPED can race with group stop start logic and then confuse
  the TRAPPING wait in ptrace_check_attach().  ptrace_stop() is now
  called with TASK_RUNNING.

* Suggested using signal->wait_chldexit instead of bit wait.

* Spotted a race condition between TRACED transition and clearing of
  TRAPPING.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>

This wake_up_state() has a turbulent history.  This is a remnant from
ancient ptrace implementation and patently wrong.  Commit 95a3540d
(ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic) removed
it but the change was reverted later by commit edaba2c5 (ptrace:
revert "ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic")
citing compatibility breakage and general brokeness of the whole group
stop / ptrace interaction.  Then, recently, it got converted from
wake_up_process() to wake_up_state() to make it less dangerous.

Digging through the mailing archives, the compatibility breakage
doesn't seem to be critical in the sense that the behavior isn't well
defined or reliable to begin with and it seems to have been agreed to
remove the wakeup with proper cleanup of the whole thing.

Now that the group stop and its interaction with ptrace are being
cleaned up, it's high time to finally kill this silliness.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>

They are only used inside kernel/ptrace.c, and have been for a long
time.  We don't want to go back to the bad-old-days when architectures
did things on their own, so make them static and private.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The wake_up_process() call in ptrace_detach() is spurious and not
interlocked with the tracee state.  IOW, the tracee could be running or
sleeping in any place in the kernel by the time wake_up_process() is
called.  This can lead to the tracee waking up unexpectedly which can be
dangerous.

The wake_up is spurious and should be removed but for now reduce its
toxicity by only waking up if the tracee is in TRACED or STOPPED state.

This bug can possibly be used as an attack vector.  I don't think it
will take too much effort to come up with an attack which triggers oops
somewhere.  Most sleeps are wrapped in condition test loops and should
be safe but we have quite a number of places where sleep and wakeup
conditions are expected to be interlocked.  Although the window of
opportunity is tiny, ptrace can be used by non-privileged users and with
some loading the window can definitely be extended and exploited.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NRoland McGrath <roland@redhat.com>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Oleg Nesterov pointed out we have to prevent multiple-threads-inside-exec
itself and we can reuse ->cred_guard_mutex for it.  Yes, concurrent
execve() has no worth.

Let's move ->cred_guard_mutex from task_struct to signal_struct.  It
naturally prevent multiple-threads-inside-exec.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use new 'datavp' and 'datalp' variables to remove unnecesary castings.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since userspace API of ptrace syscall defines @addr and @data as void
pointers, it would be more appropriate to define them as unsigned long in
kernel.  Therefore related functions are changed also.

'unsigned long' is typically used in other places in kernel as an opaque
data type and that using this helps cleaning up a lot of warnings from
sparse.
Suggested-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

exit_ptrace() releases and regrabs tasklist_lock but was missing proper
annotation.  Add it.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

exit_ptrace() takes tasklist_lock unconditionally.  We need this lock to
avoid the race with ptrace_traceme(), it acts as a barrier.

Change its caller, forget_original_parent(), to call exit_ptrace() under
tasklist_lock.  Change exit_ptrace() to drop and reacquire this lock if
needed.

This allows us to add the fastpath list_empty(ptraced) check.  In the
likely no-tracees case exit_ptrace() just returns and we avoid the lock()
+ unlock() sequence.

"Zhang, Yanmin" <yanmin_zhang@linux.intel.com> suggested to add this
check, and he reports that this change adds about 11% improvement in some
tests.
Suggested-and-tested-by: N"Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that Mike Frysinger unified the FDPIC ptrace code, we can fix the
unsafe usage of child->mm in ptrace_request(PTRACE_GETFDPIC).

We have the reference to task_struct, and ptrace_check_attach() verified
the tracee is stopped.  But nothing can protect from SIGKILL after that,
we must not assume child->mm != NULL.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NMike Frysinger <vapier.adi@gmail.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Greg Ungerer <gerg@snapgear.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The Blackfin/FRV/SuperH guys all have the same exact FDPIC ptrace code in
their arch handlers (since they were probably copied & pasted).  Since
these ptrace interfaces are an arch independent aspect of the FDPIC code,
unify them in the common ptrace code so new FDPIC ports don't need to copy
and paste this fundamental stuff yet again.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Acked-by: NRoland McGrath <roland@redhat.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NPaul Mundt <lethal@linux-sh.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>